Background: At least one anode rod is installed in
every water heater to provide corrosion protection for the
tank. Certain water conditions will cause a reaction
between this rod and the water, causing the hot water to
assume a “rotten egg” smell. The odor results from
hydrogen sulphide gas becoming dissolved in the water.

What to do: For the odor to develop, four factors
must be present (1) a concentration of sulphate in the sup
ply water, (2) little or no dissolved oxygen in the water,
(3) a sulphate- reducing bacteria within the water heater
(a harmless bacteria non-toxic to humans), and (4) an
excess of active hydrogen in the tank.
To remedy, do not simply remove the
anode(s), leaving the tank unprotected. The odor
may be reduced or eliminated in some water heaters by
replacing the anode(s) with types that have less active
material, and then chlorinating the water heater tank and
all hot water lines. Check with the manufacturer or dealer
for replacement anodes and chlorination equipment.

Special advice: Hydrogen is generated by the
corrosion-protective anode, and hydrogen gas can build up
in a hot water system unused for 2 weeks or more. This gas
is extremely flammable and explosive. As a precautionary
measure, open the hot water faucet for several minutes at
the kitchen sink before connecting any electrical
appliance to the hot water system (such as a dish washer
or a washing machine). If hydrogen gas is present, there
will likely be a sound similar to air escaping through the
pipe. Do not smoke or have any open
flame near the faucet when you open it.

Helpful hint: If
smelly water persists after anode replacement and
chlorination treatment, consider in stalling continuous
chlorination and filtering conditioning equipment to
reduce the problem.